This invention relates to a barometric meter, and more particularly a barometer or a barometric altimeter in which a displacement of a vacuum chamber is detected and displayed as a change in atmospheric air pressure or barometric altimeter.
One example of a conventional barometer utilizing the elastisity of a movable portion of an evacuated vacuum chamber is known from Japanese Patent Laid-Open No. 61-207941, in which an elastic distorsion or displacement of the vacuum chamber due to the pressure change is enlarged by a fulcrum mechanism to be indicated on a dial plate.
Also, in Japanese Patent Laid-Open No. 54-4181 and Japanese U. M. Laid-Open No. 61-36, a barometer of a structure is disclosed, in which the displacement of a vacuum chamber is converted into an electrical signal by using an electric pen which is fixed to the vacuum chamber and in sliding contact with the surface of an electric resistor to indicate electric resistance corresponding to the position of the pen.
The conventional barometric meter as above described comprises a mechanical moving part which moves in accordance with the elastic deformation of the movable portion of the vacuum chamber and an output part which outputs a barometric measurement such as a pointer on a dial panel or a slider, etc. of an electric resistor. The moving part and the output part are connected directly or through an interlocking mechanism.
In such structure, the play in the mechanically connected moving parts, the friction in the moving mechanism and the movable pointer and slider, the irregularity of the contact resistance of the slider, etc. are all causes of errors, so that a slight pressure change cannot be precisely measured and the device is not suitable for fixed-point barometric measurement on the ground.
Further, when the indicated value is to be read, it has been usual and necessary practice to hit the barometer with a finger to apply a small shock to it in order to prevent that any moving part is caught due to friction or play and that the pointer indicates an incorrect value.